[Linux-kernel-mentees] [RFC, WIP, v2 3/3] media: dvb_dummy_fe.c: write PSI information into DMX buffer

Mauro Carvalho Chehab mchehab+huawei at kernel.org
Fri Mar 27 16:48:55 UTC 2020


Em Mon, 23 Mar 2020 09:57:32 -0300
"Daniel W. S. Almeida" <dwlsalmeida at gmail.com> escreveu:

> From: "Daniel W. S. Almeida" <dwlsalmeida at gmail.com>
> 
> Periodically feed the demux with PSI packets. This is needed so userspace
> apps can retrieve information about the Transport Stream and eventually
> tune into a (dummy) channel.
> 
> Currently this commit adds support for working with 3 PSI tables:
> PAT, PMT and SDT. A dummy service with a dummy program is hardcoded
> in the driver code.

As we talked via IRC in priv, the best would be to implement the MPEG_TS
generator as part of the bridge DVB driver.

Anyway, I will review the code below assuming that you'll be moving the
implementation to the right place.

PS.: I didn't actually check if the tables are filled properly. This is
something that we can do later, once the code is running.


> 
> Signed-off-by: Daniel W. S. Almeida <dwlsalmeida at gmail.com>
> ---
>  drivers/media/dvb-frontends/Makefile          |   1 +
>  drivers/media/dvb-frontends/dvb_dummy_fe.c    | 265 ++++-
>  drivers/media/dvb-frontends/dvb_dummy_fe.h    |  32 +
>  .../media/dvb-frontends/dvb_dummy_fe_common.h |  55 ++
>  .../media/dvb-frontends/dvb_dummy_fe_psi.c    | 902 ++++++++++++++++++
>  .../media/dvb-frontends/dvb_dummy_fe_psi.h    | 287 ++++++
>  6 files changed, 1522 insertions(+), 20 deletions(-)
>  create mode 100644 drivers/media/dvb-frontends/dvb_dummy_fe_common.h
>  create mode 100644 drivers/media/dvb-frontends/dvb_dummy_fe_psi.c
>  create mode 100644 drivers/media/dvb-frontends/dvb_dummy_fe_psi.h
> 
> diff --git a/drivers/media/dvb-frontends/Makefile b/drivers/media/dvb-frontends/Makefile
> index e9179162658c..2a44239de74d 100644
> --- a/drivers/media/dvb-frontends/Makefile
> +++ b/drivers/media/dvb-frontends/Makefile
> @@ -15,6 +15,7 @@ stv0900-objs := stv0900_core.o stv0900_sw.o
>  drxd-objs := drxd_firm.o drxd_hard.o
>  cxd2820r-objs := cxd2820r_core.o cxd2820r_c.o cxd2820r_t.o cxd2820r_t2.o
>  drxk-objs := drxk_hard.o
> +dvb_dummy_fe-objs := dvb_dummy_fe_psi.o
>  
>  obj-$(CONFIG_DVB_PLL) += dvb-pll.o
>  obj-$(CONFIG_DVB_STV0299) += stv0299.o
> diff --git a/drivers/media/dvb-frontends/dvb_dummy_fe.c b/drivers/media/dvb-frontends/dvb_dummy_fe.c
> index 14446f2bdcde..ff0c510bdff5 100644
> --- a/drivers/media/dvb-frontends/dvb_dummy_fe.c
> +++ b/drivers/media/dvb-frontends/dvb_dummy_fe.c
> @@ -14,14 +14,8 @@
>  
>  #include <media/dvb_frontend.h>
>  #include "dvb_dummy_fe.h"
> -
> -
> -struct dvb_dummy_fe_cnr_to_qual_s {
> -	/* attempt to use the same values as libdvbv5 */
> -	u32 modulation;
> -	u32 fec;
> -	u32 cnr_ok, cnr_good;
> -};
> +#include "dvb_dummy_fe_common.h"
> +#include "dvb_dummy_fe_psi.h"
>  
>  struct dvb_dummy_fe_cnr_to_qual_s dvb_dummy_fe_c_cnr_2_qual[] = {
>  	/* from libdvbv5 source code, in milli db */
> @@ -73,18 +67,248 @@ static struct dvb_dummy_fe_cnr_to_qual_s dvb_dummy_fe_t_cnr_2_qual[] = {
>  	{ QAM_64, FEC_7_8, 22000, 24000},
>  };
>  
> -struct dvb_dummy_fe_config {
> -	/* probability of losing the lock due to low snr */
> -	u8 drop_tslock_prob_on_low_snr;
> -	u8 recover_tslock_prob_on_good_snr;
> -};
> +static void
> +dvb_dummy_fe_init_channels(struct dvb_dummy_channel channels[NUM_CHANNELS])
> +{
> +	const u16 pac_service_id = 0x880;
> +	const u16 pac_program_num = 0x880;
> +	const u16 pac_program_pid = 0x101; /* packet id for PMT*/
> +	const u16 pac_audio_stream_id = 0x111;
> +
> +	struct dvb_dummy_channel pac; /* PCM Audio Channel */
> +	struct dvb_dummy_table_sdt_service *pac_service;
> +	struct dvb_dummy_desc_service *pac_s_desc;
> +	u16 desc_length;
> +
> +	pac_service = dummy_fe_sdt_service_init(NULL, pac_service_id);
> +
> +	pac_s_desc = (struct dvb_dummy_desc_service *)
> +		     dummy_fe_desc_init(NULL,
> +					SERVICE_DESCRIPTOR,
> +					sizeof(*pac_s_desc));
> +
> +	pac_s_desc->name = "Sine Wave PCM Audio";
> +	pac_s_desc->service_type = DIGITAL_TELEVISION_SERVICE;
> +	pac_s_desc->length = 8 /* u8 service_type */
> +			     + strlen(pac_s_desc->name)
> +			     + strlen(pac_s_desc->name_emph)
> +			     + strlen(pac_s_desc->provider)
> +			     + strlen(pac_s_desc->provider_emph);

Please use a define for the "8" magic number, like

	#define SDT_HEADER_SIZE 8

(or something like that)


Then the above would be::

	pac_s_desc->length = SDT_HEADER_SIZE
			     + strlen(pac_s_desc->name)
			     + strlen(pac_s_desc->name_emph)
			     + strlen(pac_s_desc->provider)
			     + strlen(pac_s_desc->provider_emph);
	
Please do the same for other similar header sizes you may need.


> +
> +	dummy_fe_desc_assign((struct dvb_dummy_desc *)
> +				   pac_s_desc,
> +				   (struct dvb_dummy_desc *)
> +				   pac_service->descriptor,
> +				   &desc_length);

Please fix the alignments. it shold be, instead:

	dummy_fe_desc_assign((struct dvb_dummy_desc *) pac_s_desc,
			     (struct dvb_dummy_desc *) pac_service->descriptor,
			     &desc_length);

Yet, there's no need to do explicit typecasts. Please change the above
to:

	dummy_fe_desc_assign(pac_s_desc, pac_service->descriptor,
			     &desc_length);


> +
> +	pac_service->desc_length = desc_length;
> +
> +	pac.transport_stream_id = TRANSPORT_STREAM_ID;
> +
> +	pac.program = dummy_fe_pat_program_init(NULL,
> +						pac_service_id,
> +						pac_program_pid);
> +
> +	pac.program_num = pac_program_num;
> +	pac.streams = dummy_fe_pmt_stream_init(NULL,
> +					       ISO_IEC_13818_3_AUDIO,
> +					       pac_audio_stream_id);
> +
> +	memcpy(&channels[0], &pac, sizeof(struct dvb_dummy_channel));
> +}
>  
> -struct dvb_dummy_fe_state {
> -	struct dvb_frontend frontend;
> -	struct dvb_dummy_fe_config config;
> -	struct delayed_work poll_snr;
> -	enum fe_status status;
> -};
> +static void
> +dvb_dummy_fe_channels_destroy(struct dvb_dummy_channel channels[NUM_CHANNELS])
> +{
> +	u32 i;
> +	struct dvb_dummy_channel *curr;
> +
> +	for (i = 0; i < NUM_CHANNELS; ++i) {
> +		curr = &channels[i];
> +		dummy_fe_sdt_service_destroy(curr->service);
> +		dummy_fe_pat_program_destroy(curr->program);
> +		dummy_fe_pmt_stream_destroy(curr->streams);
> +	}
> +}
> +
> +static struct dvb_dummy_table_sdt_service*
> +dummy_fe_sdt_serv_cat_into_new(struct dvb_dummy_channel channels[NUM_CHANNELS])
> +{
> +	u32 i;
> +	struct dvb_dummy_table_sdt_service *curr = NULL;
> +	struct dvb_dummy_table_sdt_service *head = NULL;
> +	struct dvb_dummy_table_sdt_service *tail = NULL;
> +	u16 service_id;
> +
> +	for (i = 0; i < NUM_CHANNELS; ++i) {
> +		curr = channels[i].service;
> +		service_id = curr->service_id;
> +
> +		if (!curr)
> +			continue;
> +
> +		while (curr->next) {
> +			tail = dummy_fe_sdt_service_init(tail, service_id);
> +
> +			if (!head)
> +				head = tail;
> +
> +			curr = curr->next;
> +		}
> +	}
> +
> +	return head;
> +}
> +
> +static struct dvb_dummy_table_pat_program*
> +dummy_fe_pat_prog_cat_into_new(struct dvb_dummy_channel channels[NUM_CHANNELS])
> +{
> +	u32 i;
> +	struct dvb_dummy_table_pat_program *curr = NULL;
> +	struct dvb_dummy_table_pat_program *head = NULL;
> +	struct dvb_dummy_table_pat_program *tail = NULL;
> +
> +	for (i = 0; i < NUM_CHANNELS; ++i) {
> +		curr = channels[i].program;
> +
> +		if (!curr)
> +			continue;
> +
> +		while (curr->next) {
> +			tail = dummy_fe_pat_program_init
> +			       (tail, curr->service_id, curr->pid);

Please do, instead:

			tail = dummy_fe_pat_program_init(tail,
							  curr->service_id,
							  curr->pid);


> +
> +			if (!head)
> +				head = tail;
> +
> +			curr = curr->next;
> +		}
> +	}
> +
> +	return head;
> +}
> +
> +static void
> +dummy_fe_pmt_stream_match_with_sections(struct dvb_dummy_channel *channels,
> +					struct dvb_dummy_table_pmt *sections,
> +					u32 nsections)

Please align the parenthesis.

I would actually rename it, as the name is too big for my taste.
I suspect that this name would be good enough:

	dummy_fe_pmt_match_sections()



> +{
> +	struct dvb_dummy_table_pmt *curr_section = NULL;
> +	u32 i, j;
> +
> +	for (i = 0; i < NUM_CHANNELS; ++i) {
> +		for (j = 0; j < nsections; ++j) {
> +			curr_section = &sections[j];
> +
> +			if (!curr_section)
> +				continue;
> +
> +			if (curr_section->header.id ==
> +			    channels[i].program_num) {
> +				dummy_fe_pmt_stream_assign(curr_section,
> +							   channels[i].streams);
> +				break;
> +			}
> +		}
> +	}
> +}
> +
> +static void dvb_dummy_fe_thread_mpeg_ts_tick(struct dvb_frontend *fe)
> +{
> +	struct dvb_dummy_fe_state *state = fe->demodulator_priv;
> +	const unsigned int SLEEP_MSECS = 10;
> +	u32 ticks = 0;
> +	u32 i;
> +	char *buf = kzalloc(DMX_BUF_LEN, GFP_KERNEL);
> +	u32 buffer_offset;
> +
> +	struct dvb_dummy_table_pat pat = {0};
> +	struct dvb_dummy_table_sdt sdt = {0};

I guess it is ok here, but allocating too much stuff at the stack is
dangerous. Linux Kernel stack is very small. Perhaps the best would
be to place those at the driver's private struct (with is allocated with
kalloc).

> +
> +	struct dvb_dummy_table_pmt *pmt_sections;
> +
> +	struct dvb_dummy_table_pat_program *programs = NULL;
> +	struct dvb_dummy_table_sdt_service *services = NULL;
> +
> +	bool update_version_num = false;
> +	u16 pmt_pid;
> +
> +	programs = dummy_fe_pat_prog_cat_into_new(state->channels);
> +	services = dummy_fe_sdt_serv_cat_into_new(state->channels);
> +
> +	/* assemble all programs and assign to PAT */
> +	dummy_fe_pat_program_assign(&pat, programs);
> +
> +	/* assemble all services and assign to SDT */
> +	dummy_fe_sdt_service_assign(&sdt, services);
> +
> +	/* a section for each program_id */
> +	pmt_sections = kcalloc(pat.programs,
> +			       sizeof(struct dvb_dummy_table_pmt),
> +			       GFP_KERNEL);
> +
> +	dummy_fe_pmt_create_section_for_each_pat_entry(&pat,
> +						       pmt_sections);
> +
> +	dummy_fe_pmt_stream_match_with_sections(state->channels,
> +						pmt_sections,
> +						pat.programs);
> +
> +	dummy_fe_pat_table_init(&pat,
> +				update_version_num,
> +				TRANSPORT_STREAM_ID);
> +
> +	dummy_fe_sdt_table_init(&sdt,
> +				update_version_num,
> +				TRANSPORT_STREAM_ID);
> +	while (true) {
> +		memset(buf, 0, DMX_BUF_LEN);
> +		buffer_offset = 0;
> +
> +		if ((ticks % 50) == 0) {
> +			/* push PSI packets into the buffer */
> +
> +			buffer_offset +=
> +				dummy_fe_pat_write_into(buf,
> +							buffer_offset,
> +							&pat);
> +			for (i = 0; i < pat.programs; ++i) {
> +				pmt_pid =
> +				dummy_fe_pmt_get_pid(&pmt_sections[i],
> +						     &pat);
> +
> +				/* not found */
> +				WARN_ON(pmt_pid > LAST_VALID_TS_PID);
> +
> +				/* write each section into buffer */
> +				buffer_offset +=
> +				dummy_fe_pmt_write_into(buf,
> +							buffer_offset,
> +							&pmt_sections[i],
> +							pmt_pid);
> +			}
> +
> +			buffer_offset +=
> +				dummy_fe_sdt_write_into(buf,
> +							buffer_offset,
> +							&sdt);
> +
> +			WARN_ON(buffer_offset > DMX_BUF_LEN); /* overflow */

> +			msleep_interruptible(SLEEP_MSECS);

That doesn't sound right, for two reasons:

1) msleep_interruptible() can take less time than expected, if
   interupted;
2) the time may vary a lot.

I would use the high-res timer here, giving a range for it (maybe a 10ms
range?), e. g., something like:

			usleep_range(SLEEP_USECS, SLEEP_USECS + 10000);



> +		}
> +	}
> +
> +	dummy_fe_pat_table_destroy(&pat);
> +	dummy_fe_sdt_table_destroy(&sdt);
> +
> +	for (i = 0; i < pat.programs; ++i) {
> +		/* destroy all PMT sections */
> +		dummy_fe_pmt_table_destroy(&pmt_sections[i]);
> +		kfree(&pmt_sections[i]);
> +	}
> +
> +	kfree(buf);

The above code will never be called, as there's an infinite loop at the
task.

Either you should do something like:

	while(st->psi_running) {
		...
	}
	/* Free code */

or rewrite it and use some something like kthread, workqueue, ...

> +}



>  
>  static void poll_snr_handler(struct work_struct *work)
>  {
> @@ -165,7 +389,6 @@ static void poll_snr_handler(struct work_struct *work)
>  static int dvb_dummy_fe_read_status(struct dvb_frontend *fe,
>  				    enum fe_status *status)
>  {
> -
>  	struct dvb_dummy_fe_state *state = fe->demodulator_priv;
>  
>  	*status = state->status;
> @@ -232,6 +455,7 @@ static int dvb_dummy_fe_init(struct dvb_frontend *fe)
>  {
>  	struct dvb_dummy_fe_state *state = fe->demodulator_priv;
>  
> +	dvb_dummy_fe_init_channels(state->channels);
>  	INIT_DELAYED_WORK(&state->poll_snr, &poll_snr_handler);
>  	schedule_delayed_work(&state->poll_snr, msecs_to_jiffies(2000));
>  	return 0;
> @@ -254,6 +478,7 @@ static void dvb_dummy_fe_release(struct dvb_frontend *fe)
>  	struct dvb_dummy_fe_state *state = fe->demodulator_priv;
>  
>  	cancel_delayed_work_sync(&state->poll_snr);
> +	dvb_dummy_fe_channels_destroy(state->channels);
>  	kfree(state);
>  }
>  
> diff --git a/drivers/media/dvb-frontends/dvb_dummy_fe.h b/drivers/media/dvb-frontends/dvb_dummy_fe.h
> index 463abf5ebd56..02efa1aed09c 100644
> --- a/drivers/media/dvb-frontends/dvb_dummy_fe.h
> +++ b/drivers/media/dvb-frontends/dvb_dummy_fe.h
> @@ -10,6 +10,38 @@
>  
>  #include <linux/dvb/frontend.h>
>  #include <media/dvb_frontend.h>
> +#include "dvb_dummy_fe_common.h"
> +#include "dvb_dummy_fe_psi.h"
> +
> +struct dvb_dummy_fe_cnr_to_qual_s {
> +	/* attempt to use the same values as libdvbv5 */
> +	u32 modulation;
> +	u32 fec;
> +	u32 cnr_ok, cnr_good;
> +};
> +
> +struct dvb_dummy_channel {
> +	u16 transport_stream_id;
> +	struct dvb_dummy_table_sdt_service *service;
> +	u16 program_num;
> +	/* a single program with one or more streams associated with it */
> +	struct dvb_dummy_table_pat_program *program;
> +	struct dvb_dummy_table_pmt_stream *streams;
> +};
> +
> +struct dvb_dummy_fe_config {
> +	/* prob of losing the lock due to low snr */
> +	u8 drop_tslock_prob_on_low_snr;
> +	u8 recover_tslock_prob_on_good_snr;
> +};
> +
> +struct dvb_dummy_fe_state {
> +	struct dvb_frontend frontend;
> +	struct dvb_dummy_fe_config config;
> +	struct delayed_work poll_snr;
> +	enum fe_status status;
> +	struct dvb_dummy_channel channels[NUM_CHANNELS];
> +};
>  
>  #if IS_REACHABLE(CONFIG_DVB_DUMMY_FE)
>  struct dvb_frontend *dvb_dummy_fe_ofdm_attach(void);
> diff --git a/drivers/media/dvb-frontends/dvb_dummy_fe_common.h b/drivers/media/dvb-frontends/dvb_dummy_fe_common.h
> new file mode 100644
> index 000000000000..c43b24e2b363
> --- /dev/null
> +++ b/drivers/media/dvb-frontends/dvb_dummy_fe_common.h
> @@ -0,0 +1,55 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef DVB_DUMMY_FE_PRIV_H
> +#define DVB_DUMMY_FE_PRIV_H
> +
> +#include <linux/types.h>
> +#include <media/dvb_frontend.h>
> +
> +#define CRC_SIZE_IN_BYTES 32
> +#define NUM_CHANNELS 1
> +#define TRANSPORT_STREAM_ID 0x744 /* a single stream */
> +#define TS_SYNC_BYTE 0x47
> +#define TS_PACKET_LEN 188
> +#define TS_PAYLOAD_LEN 184
> +#define DMX_BUF_LEN (20 * TS_PACKET_LEN)
> +#define LAST_VALID_TS_PID 8191
> +
> +/* to be used by both PSI and ES */
> +struct dvb_dummy_mpeg_ts_adaption {
> +	u8 length;
> +	struct {
> +		u8 extension:1;
> +		u8 private_data:1;
> +		u8 splicing_point:1;
> +		u8 OPCR:1;
> +		u8 PCR:1;
> +		u8 priority:1;
> +		u8 random_access:1;
> +		u8 discontinued:1;
> +	} __packed;
> +	u8 data[];
> +} __packed;
> +
> +/* to be used by both PSI and ES */
> +struct dvb_dummy_mpeg_ts {
> +	u8 sync_byte;
> +	union {
> +		u16 bitfield;
> +		struct {
> +			u16 pid:13;
> +			u16 priority:1;
> +			u16 payload_start:1;
> +			u16 tei:1;
> +		} __packed;
> +	} __packed;
> +	struct {
> +		u8 continuity_counter:4;
> +		u8 payload:1;
> +		u8 adaptation_field:1;
> +		u8 scrambling:2;
> +	} __packed;
> +	struct dvb_dummy_mpeg_ts_adaption adaption[];
> +} __packed;
> +
> +#endif // DVB_DUMMY_FE_PRIV_H
> \ No newline at end of file
> diff --git a/drivers/media/dvb-frontends/dvb_dummy_fe_psi.c b/drivers/media/dvb-frontends/dvb_dummy_fe_psi.c
> new file mode 100644
> index 000000000000..8cf0fc1e584e
> --- /dev/null
> +++ b/drivers/media/dvb-frontends/dvb_dummy_fe_psi.c
> @@ -0,0 +1,902 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/types.h>
> +#include <linux/string.h>
> +#include <linux/slab.h>
> +#include <linux/crc32.h>
> +#include <linux/string.h>
> +
> +#include "dvb_dummy_fe_common.h"
> +#include "dvb_dummy_fe_psi.h"
> +
> +static u32 dummy_fe_ts_psi_write_stuffing(void *to, u32 len)
> +{
> +	memset(to, 0xff, len);
> +	return len;
> +}
> +
> +static u32
> +dummy_fe_ts_psi_write_into(struct psi_write_args args)
> +{
> +	/*
> +	 * Packetize PSI sections into TS packets:
> +	 *  push a TS header (4bytes) every 184 bytes
> +	 *  manage the continuity_counter
> +	 *  add stuffing after the CRC
> +	 */
> +
> +	u32 nbytes_past_boundary = (args.offset % TS_PACKET_LEN);
> +	bool aligned = nbytes_past_boundary == 0;
> +	bool split = args.len > TS_PAYLOAD_LEN;
> +	u32 payload_write_len = (split) ? TS_PAYLOAD_LEN : args.len;
> +
> +	struct psi_write_args new_args = {0};
> +	struct dvb_dummy_mpeg_ts ts_header = {0};
> +
> +	u32 nbytes = 0; /* number of bytes written by this function */
> +
> +	if (args.new_psi_section && !aligned) {
> +		/*
> +		 * must pad the buffer with the complement to get a
> +		 * multiple of 188
> +		 */
> +		nbytes += dummy_fe_ts_psi_write_stuffing(args.to +
> +							 args.offset +
> +							 nbytes,
> +							 TS_PACKET_LEN -
> +							 nbytes_past_boundary);
> +
> +		/*
> +		 * if we were not at a packet boundary, we are now after
> +		 * stuffing the buffer with 0xff
> +		 */
> +		aligned = true;
> +	}
> +
> +	if (aligned) {
> +		/* if at a packet boundary, write a new TS header */
> +		ts_header.sync_byte = TS_SYNC_BYTE;
> +		ts_header.tei = 0;
> +		ts_header.payload_start = 1;
> +		ts_header.pid = args.pid;
> +		ts_header.priority = 0;
> +		ts_header.scrambling = 0; /* not scrambled */
> +		ts_header.continuity_counter = *args.continuity_counter;
> +		ts_header.payload_start = 0; /* no adaption for now */
> +
> +		/* copy the header minus the adaption pointer*/
> +		memcpy(args.to + args.offset + nbytes,
> +		       &ts_header,
> +		       sizeof(ts_header));
> +
> +		nbytes += sizeof(ts_header);
> +	}
> +
> +	if (args.new_psi_section) {
> +		/* write the pointer_field in the first byte of the payload */
> +		memset(args.to + args.offset + nbytes, 0x0, 1);
> +		nbytes += 1;
> +		--payload_write_len; /* one byte was used by the pointer field*/
> +	}
> +
> +	/* write as much of the payload as we possibly can */
> +	memcpy(args.to + args.offset + nbytes,
> +	       args.from,
> +	       payload_write_len);
> +
> +	nbytes += payload_write_len;
> +
> +	if (split) {
> +		/*
> +		 * next TS packet keeps the same PID, but increments the
> +		 * counter
> +		 */
> +		++(*args.continuity_counter);
> +		/* 'nbytes' written from a total of 'len' requested*/
> +		args.len -= nbytes;
> +		/*
> +		 * recursively write the rest of the data until we do not
> +		 * need to split it anymore
> +		 */
> +		memcpy(&new_args, &args, sizeof(struct psi_write_args));
> +		new_args.from = args.from + nbytes;
> +		new_args.offset = args.offset + nbytes;
> +		new_args.new_psi_section = false;
> +
> +		nbytes += dummy_fe_ts_psi_write_into(new_args);
> +	}
> +
> +	if (args.is_crc)
> +		/*
> +		 * as the CRC is last in the section, stuff the rest of the
> +		 * packet if there is any remaining space in there
> +		 */
> +
> +		nbytes += dummy_fe_ts_psi_write_stuffing(args.to + nbytes,
> +							 TS_PAYLOAD_LEN -
> +							 nbytes);
> +
> +	return nbytes;
> +}
> +
> +static u32 table_section_crc32_write_into(struct crc32_write_args args)
> +{
> +	/* the CRC is the last entry in the section */
> +	u32 nbytes = 0;
> +	u32 crc;
> +	struct psi_write_args psi_args = {0};
> +
> +	crc = crc32(0, args.to, args.offset);
> +
> +	psi_args.to = args.to;
> +	psi_args.from = &crc;
> +	psi_args.len = CRC_SIZE_IN_BYTES;
> +	psi_args.offset = args.offset;
> +	psi_args.pid = args.pid;
> +	psi_args.new_psi_section = false;
> +	psi_args.continuity_counter = args.continuity_counter;
> +	psi_args.is_crc = true;
> +
> +	nbytes += dummy_fe_ts_psi_write_into(psi_args);
> +
> +	return nbytes;
> +}
> +
> +struct dvb_dummy_desc *dummy_fe_desc_init(struct dvb_dummy_desc *head,
> +					  u8 type,
> +					  u8 length)
> +{
> +	struct dvb_dummy_desc *desc;
> +
> +	/* alloc enough memory for the flexible array too */
> +	desc = kzalloc(sizeof(*desc) + length, GFP_KERNEL);
> +
> +	desc->type = type;
> +	desc->length = length;
> +
> +	if (head) {
> +		while (head->next)
> +			head = head->next;
> +
> +		head->next = desc;
> +	}
> +
> +	return desc;
> +}
> +
> +void dummy_fe_desc_destroy(struct dvb_dummy_desc *desc)
> +{
> +	struct dvb_dummy_desc *curr = desc;
> +	struct dvb_dummy_desc *tmp = NULL;
> +
> +	while (curr) {
> +		tmp = curr;
> +		curr = curr->next;
> +		kfree(tmp);
> +	}
> +}
> +
> +static u32
> +dummy_fe_desc_comp_len(struct dvb_dummy_desc *desc)
> +{
> +	u32 length = 0;
> +
> +	if (!desc)
> +		return 0;
> +
> +	while (desc) {
> +		length += desc->length;
> +		desc = desc->next;
> +	}
> +
> +	return length;
> +}
> +
> +void dummy_fe_desc_assign(struct dvb_dummy_desc *desc,
> +			  struct dvb_dummy_desc *desc_ptr,
> +			  u16 *desc_length)
> +{
> +	if (desc_ptr)
> +		/* clean the old data */
> +		dummy_fe_desc_destroy(desc_ptr);

Never do that:

	if (foo)
		/* some comment */
		something();

This will very easily get sideways, if one wants to add more stuff at
the if. We usually, just do, instead:

	/* clean the old data */
	if (desc_ptr)
		dummy_fe_desc_destroy(desc_ptr);


> +
> +	*desc_length = dummy_fe_desc_comp_len(desc);
> +	desc_ptr = desc;
> +}
> +
> +static u32 dummy_fe_desc_write_into(struct desc_write_args args)
> +{
> +	u32 nbytes = 0; /* the number of bytes written by this function */
> +	struct psi_write_args psi_args = {0};
> +
> +	psi_args.to = args.to;
> +	psi_args.from = args.desc;
> +	psi_args.len = 16; /* u8 type + u8 length */
> +	psi_args.offset = args.offset;
> +	psi_args.pid = args.pid;
> +	psi_args.new_psi_section = false;
> +	psi_args.continuity_counter = args.continuity_counter;
> +	psi_args.is_crc = false;
> +
> +	nbytes += dummy_fe_ts_psi_write_into(psi_args);
> +
> +	/* move 'from' pointer to point to u8 data[] */
> +	psi_args.from = args.desc + nbytes + sizeof(struct dvb_dummy_desc *);
> +	psi_args.len = args.desc->length;
> +	psi_args.offset = args.offset + nbytes;
> +
> +	nbytes += dummy_fe_ts_psi_write_into(psi_args);
> +
> +	return nbytes;
> +}
> +
> +static u32
> +dummy_fe_table_header_write_into(struct header_write_args args)
> +{
> +	/* the number of bytes written by this function */
> +	u32 nbytes = 0;
> +	struct psi_write_args psi_args = {0};
> +
> +	psi_args.to = args.to;
> +	psi_args.from = args.h;
> +	psi_args.len = sizeof(struct dvb_dummy_table_header);
> +	psi_args.offset = args.offset;
> +	psi_args.pid = args.pid;
> +	psi_args.new_psi_section = true;
> +	psi_args.continuity_counter = args.continuity_counter;
> +	psi_args.is_crc = false;
> +
> +	nbytes += dummy_fe_ts_psi_write_into(psi_args);
> +
> +	return nbytes;
> +}
> +
> +static u16
> +dummy_fe_pat_table_comp_sec_len(struct dvb_dummy_table_pat *pat)
> +{
> +	/* see ISO/IEC 13818-1 : 2000 p.43 */
> +	u16 length = 0;
> +	u32 i;
> +
> +	/* from immediately after 'section_length' until 'last_section_number'*/
> +	length += PAT_LEN_UNTIL_LAST_SECTION_NUMBER;
> +
> +	for (i = 0; i < pat->programs; ++i)
> +		/* do not count the pointer */
> +		length += sizeof(struct dvb_dummy_table_pat_program) -
> +			  sizeof(struct dvb_dummy_table_pat_program *);
> +
> +	length += CRC_SIZE_IN_BYTES;
> +
> +	WARN_ON(length > PAT_MAX_SECTION_LEN);
> +	return length;
> +}
> +
> +static u16
> +dummy_fe_pmt_table_comp_sec_len(struct dvb_dummy_table_pmt *pmt)
> +{
> +	/* see ISO/IEC 13818-1 : 2000 p.46 */
> +	u16 length = 0;
> +	struct dvb_dummy_table_pmt_stream *s = pmt->stream;
> +
> +	/* from immediately after 'section_length' until 'program_info_length'*/
> +	length += PMT_LEN_UNTIL_PROGRAM_INFO_LENGTH;
> +
> +	/* do not fail if 'desc_length' has not been computed yet */
> +	length += dummy_fe_desc_comp_len(pmt->descriptor);
> +	length += pmt->desc_length;
> +
> +	while (s) {
> +		/* skip both pointers at the end */
> +		length += sizeof(struct dvb_dummy_table_pmt_stream) -
> +			  sizeof(struct dvb_dummy_desc *) -
> +			  sizeof(struct dvb_dummy_table_pmt_stream *);
> +
> +		length += dummy_fe_desc_comp_len(s->descriptor);
> +		s = s->next;
> +	}
> +
> +	length += CRC_SIZE_IN_BYTES;
> +
> +	WARN_ON(length > PMT_MAX_SECTION_LEN);
> +	return length;
> +}
> +
> +static u16
> +dummy_fe_sdt_table_comp_sec_len
> +(struct dvb_dummy_table_sdt *sdt)
> +{
> +	/* see ETSI EN 300 468 V 1.10.1 p.24 */
> +	u16 length = 0;
> +	struct dvb_dummy_table_sdt_service *s = sdt->service;
> +
> +	/*
> +	 * from immediately after 'section_length' until
> +	 * 'reserved_for_future_use'
> +	 */
> +	length += SDT_LEN_UNTIL_RESERVED_FOR_FUTURE_USE;
> +
> +	while (s) {
> +		/* skip both pointers at the end */
> +		length += sizeof(struct dvb_dummy_table_pmt_stream) -
> +			  sizeof(struct dvb_dummy_desc *) -
> +			  sizeof(struct dvb_dummy_table_pmt_stream *);
> +		/* do not fail if 'desc_length' has not been computed yet */
> +		length += dummy_fe_desc_comp_len(s->descriptor);

There's something really weird here: "s" var is not modified here,
so the while() will always be true (or false).

> +	}
> +
> +	length += CRC_SIZE_IN_BYTES;
> +
> +	WARN_ON(length > SDT_MAX_SECTION_LEN);

even assuming that you fix the above code, and update "s" to the next
SDT data, this is still too dangerous: if are there any risk of going 
past the buffer size, you should check *before* the bad condition happens,
e. g., something like:

	while (s && length + CRC_SIZE_IN_BYTES < SDT_MAX_SECTION_LEN) {
		...
	}

	if (s)
		WARN_ON(length > SDT_MAX_SECTION_LEN);

> +	return length;
> +}
> +
> +struct dvb_dummy_table_pat_program*
> +dummy_fe_pat_program_init(struct dvb_dummy_table_pat_program *head,
> +			  u16 service_id,
> +			  u16 pid)
> +{
> +	struct dvb_dummy_table_pat_program *program;
> +
> +	program = kzalloc(sizeof(*program), GFP_KERNEL);
> +
> +	program->service_id = service_id;
> +	program->pid = pid; /* pid for the PMT section in the TS */
> +	program->next = NULL;
> +	program->reserved = 0x7;
> +
> +	if (head) {
> +		while (head->next)
> +			head = head->next;
> +
> +		head->next = program;
> +	}
> +
> +	return program;
> +}
> +
> +void
> +dummy_fe_pat_program_destroy(struct dvb_dummy_table_pat_program *p)
> +{
> +	struct dvb_dummy_table_pat_program *curr = p;
> +	struct dvb_dummy_table_pat_program *tmp = NULL;
> +
> +	while (curr) {
> +		tmp = curr;
> +		curr = curr->next;
> +		kfree(tmp);
> +	}
> +}
> +
> +void
> +dummy_fe_pat_program_assign(struct dvb_dummy_table_pat *pat,
> +			    struct dvb_dummy_table_pat_program *p)
> +{
> +	u16 program_count = 0;
> +	struct dvb_dummy_table_pat_program *program = p;
> +
> +	if (pat->program)
> +		dummy_fe_pat_program_destroy(pat->program);
> +
> +	while (program) {
> +		++program_count;
> +		program = program->next;
> +	}
> +
> +	pat->programs = program_count;
> +
> +	/* Recompute section length */
> +	pat->header.section_length = dummy_fe_pat_table_comp_sec_len(pat);
> +
> +	pat->program = p;
> +}
> +
> +void dummy_fe_pat_table_init(struct dvb_dummy_table_pat *pat,
> +			     bool update_version_num,
> +			     u16 transport_stream_id)
> +{
> +	static u8 pat_version;
> +
> +	pat->header.table_id = 0x0;
> +	pat->header.syntax = 0x1;
> +	pat->header.zero = 0x0;
> +	pat->header.one = 0x03;
> +
> +	pat->header.id = transport_stream_id; /* transport stream ID, at will */
> +	pat->header.current_next = 0x1;
> +
> +	/* ETSI 300 468: indicates changes in the TS described by this table*/
> +	if (update_version_num)
> +		++pat_version;
> +
> +	pat->header.version = pat_version;
> +
> +	pat->header.one2 = 0x03;
> +	pat->header.section_id = 0x0;
> +	pat->header.last_section = 0x0;
> +
> +	pat->programs = 0;
> +
> +	pat->header.section_length = dummy_fe_pat_table_comp_sec_len(pat);
> +}
> +
> +u32 dummy_fe_pat_write_into(char *buf,
> +			    u32 offset,
> +			    struct dvb_dummy_table_pat *pat)
> +{
> +	u32 nbytes = 0; /* the number of bytes written by this function */
> +	u8 continuity_counter = 0;
> +	const u16 pat_pid = pat->header.table_id; /* always 0x0 */
> +
> +	struct dvb_dummy_table_pat_program *p = pat->program;
> +	struct header_write_args h_args = {0};
> +	struct psi_write_args args = {0};
> +	struct crc32_write_args c_args = {0};

How much data are you allocating here at the small Linux stack?

> +
> +	h_args.to = buf;
> +	h_args.offset = offset;
> +	h_args.h = &pat->header;
> +	h_args.pid = pat_pid;
> +	h_args.continuity_counter = &continuity_counter;
> +
> +	nbytes += dummy_fe_table_header_write_into(h_args);
> +
> +	args.to = buf;
> +	args.from = pat + sizeof(struct dvb_dummy_table_header),
> +	args.len = sizeof(pat->programs);
> +	args.offset = offset + nbytes;
> +	args.pid = pat_pid;
> +	args.new_psi_section = false;
> +	args.continuity_counter = &continuity_counter;
> +	args.is_crc = false;
> +
> +	nbytes += dummy_fe_ts_psi_write_into(args);
> +
> +	while (p) {
> +		args.from = p;
> +		/* skip the pointer */
> +		args. len = sizeof(*p) -
> +			    sizeof(struct dvb_dummy_table_pat_program *);
> +		args.offset = offset + nbytes;
> +
> +		nbytes += dummy_fe_ts_psi_write_into(args);
> +		p = p->next;
> +	}

Please also protect here to avoid going past the buffer size.

> +
> +	c_args.to = buf;
> +	c_args.offset = offset + nbytes;
> +	c_args.pid = pat_pid;
> +	c_args.continuity_counter = &continuity_counter;
> +
> +	nbytes += table_section_crc32_write_into(c_args);
> +
> +	return nbytes;
> +}
> +
> +void
> +dummy_fe_pat_table_destroy(struct dvb_dummy_table_pat *p)
> +{
> +	dummy_fe_pat_program_destroy(p->program);
> +}
> +
> +struct dvb_dummy_table_pmt_stream*
> +dummy_fe_pmt_stream_init(struct dvb_dummy_table_pmt_stream *head,
> +			 enum dvb_dummy_stream_types stream_type,
> +			 u16 es_pid)
> +{
> +	struct dvb_dummy_table_pmt_stream *stream;
> +
> +	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
> +
> +	stream->type = stream_type;
> +	stream->elementary_pid = es_pid;
> +	stream->reserved = 0x07;
> +
> +	stream->desc_length = dummy_fe_desc_comp_len(stream->descriptor);
> +
> +	stream->zero = 0x0;
> +	stream->reserved2 = 0x0f;
> +
> +	if (head) {
> +		while (head->next)
> +			head = head->next;
> +
> +		head->next = stream;
> +	}
> +
> +	return stream;
> +}
> +
> +void dummy_fe_pmt_stream_destroy(struct dvb_dummy_table_pmt_stream *s)
> +{
> +	struct dvb_dummy_table_pmt_stream *curr_stream = s;
> +	struct dvb_dummy_table_pmt_stream *tmp_stream = NULL;
> +
> +	while (curr_stream) {
> +		tmp_stream = curr_stream;
> +		curr_stream = curr_stream->next;
> +		kfree(tmp_stream);
> +	}
> +}
> +
> +void dummy_fe_pmt_stream_assign(struct dvb_dummy_table_pmt *pmt,
> +				struct dvb_dummy_table_pmt_stream *s)
> +{
> +	struct dvb_dummy_table_pmt_stream *stream = s;
> +	struct dvb_dummy_desc *desc = s->descriptor;
> +
> +	if (pmt->stream)
> +		dummy_fe_pmt_stream_destroy(pmt->stream);
> +
> +	while (stream)
> +		stream = stream->next;
> +
> +	while (desc)
> +		desc = desc->next;
> +
> +	/* Recompute section length */
> +	pmt->header.section_length = dummy_fe_pmt_table_comp_sec_len(pmt);
> +
> +	pmt->stream = s;
> +}
> +
> +u16 dummy_fe_pmt_get_pid(struct dvb_dummy_table_pmt *section,
> +			 struct dvb_dummy_table_pat *pat)
> +{
> +	struct dvb_dummy_table_pat_program *program = pat->program;
> +
> +	while (program)
> +		/*
> +		 * service_id is the same as program_number in the
> +		 * corresponding program_map_section
> +		 * see ETSI EN 300 468 v1.15.1 p. 24
> +		 */
> +		if (program->service_id == section->header.id)
> +			return pat->program->pid;
> +
> +	return LAST_VALID_TS_PID + 1; /* not found */
> +}
> +
> +void dummy_fe_pmt_table_init(struct dvb_dummy_table_pmt *pmt,
> +			     bool update_version_num,
> +			     u16 program_number,
> +			     u16 pcr_pid)
> +{
> +	static u8 pmt_version;
> +
> +	pmt->header.table_id = 0x2;
> +	pmt->header.syntax = 0x1;
> +	pmt->header.zero = 0x0;
> +	pmt->header.one = 0x3;
> +
> +	pmt->header.id = program_number;
> +	pmt->header.current_next = 0x1;
> +
> +	/* ETSI 300 468: indicates changes in the TS described by this table*/
> +	if (update_version_num)
> +		++pmt_version;
> +
> +	pmt->header.version = pmt_version;
> +
> +	pmt->header.one2 = 0x3;
> +	pmt->header.section_id = 0;
> +	pmt->header.last_section = 0;
> +
> +	pmt->pcr_pid = (pcr_pid) ? pcr_pid : 0x1fff;
> +	pmt->reserved2 = 0x03;
> +
> +	pmt->reserved3 = 0x0f;
> +	pmt->zero3 = 0x0;
> +
> +	pmt->desc_length = dummy_fe_desc_comp_len(pmt->descriptor);
> +
> +	pmt->header.section_length = dummy_fe_pmt_table_comp_sec_len(pmt);
> +}
> +
> +u32 dummy_fe_pmt_write_into(char *buf,
> +			    u32 offset,
> +			    struct dvb_dummy_table_pmt *pmt,
> +			    u16 pid)
> +{
> +	u32 nbytes = 0; /* the number of bytes written by this function */
> +	u8 continuity_counter = 0;
> +	struct dvb_dummy_desc *table_descriptor = pmt->descriptor;
> +	struct dvb_dummy_table_pmt_stream *stream = pmt->stream;
> +	struct dvb_dummy_desc *stream_descriptor = (stream) ?
> +						    pmt->stream->descriptor :
> +						    NULL;
> +
> +	struct header_write_args h_args = {0};
> +	struct psi_write_args args = {0};
> +	struct desc_write_args d_args = {0};
> +	struct crc32_write_args c_args = {0};

same here: how much data are you allocating at the Linux small stack?

> +
> +	h_args.to = buf;
> +	h_args.offset = offset;
> +	h_args.h = &pmt->header;
> +	h_args.pid = pid;
> +	h_args.continuity_counter = &continuity_counter;
> +
> +	nbytes += dummy_fe_table_header_write_into(h_args);
> +
> +	args.to = buf;
> +	args.from = pmt + sizeof(struct dvb_dummy_table_header);
> +	args.len = 32;
> +	args.offset = offset + nbytes;
> +	args.pid = pid;
> +	args.new_psi_section = false;
> +	args.continuity_counter = &continuity_counter;
> +	args.is_crc = false;
> +
> +	nbytes += dummy_fe_ts_psi_write_into(args);
> +
> +	while (table_descriptor) {
> +		d_args.to = buf;
> +		d_args.offset = offset + nbytes;
> +		d_args.desc = table_descriptor;
> +		d_args.pid = pid;
> +		d_args.continuity_counter = &continuity_counter;
> +		nbytes += dummy_fe_desc_write_into(d_args);
> +
> +		table_descriptor = table_descriptor->next;
> +	}
> +
> +	while (stream) {
> +		args.from = stream;
> +		args.len = 40; /* u8 type + (2* u16) bitfields */
> +		args.offset = offset + nbytes;
> +
> +		nbytes += dummy_fe_ts_psi_write_into(args);
> +
> +		while (stream_descriptor) {
> +			d_args.desc = stream_descriptor;
> +			d_args.offset = offset + nbytes;
> +			nbytes += dummy_fe_desc_write_into(d_args);
> +
> +			stream_descriptor = stream_descriptor->next;
> +		}
> +
> +		stream = stream->next;
> +	}

Please protect both above loops against buffer overflow.

> +
> +	c_args.to = buf;
> +	c_args.offset = offset + nbytes;
> +	c_args.pid = pid;
> +	c_args.continuity_counter = &continuity_counter;
> +
> +	nbytes += table_section_crc32_write_into(c_args);
> +
> +	return nbytes;
> +}
> +
> +void dummy_fe_pmt_table_destroy(struct dvb_dummy_table_pmt *pmt)
> +{
> +	struct dvb_dummy_desc *curr_desc = pmt->descriptor;
> +	struct dvb_dummy_desc *tmp_desc = NULL;
> +
> +	while (curr_desc) {
> +		tmp_desc = curr_desc;
> +		curr_desc = curr_desc->next;
> +		dummy_fe_desc_destroy(tmp_desc);
> +		kfree(tmp_desc);
> +	}
> +
> +	dummy_fe_pmt_stream_destroy(pmt->stream);
> +}
> +
> +void dummy_fe_sdt_table_init(struct dvb_dummy_table_sdt *sdt,
> +			     bool update_version_num,
> +			     u16 transport_stream_id)
> +{
> +	static u8 sdt_version;
> +
> +	sdt->header.table_id = 0x42;
> +
> +	sdt->header.one = 0x3;
> +	sdt->header.zero = 0x1;
> +	/*
> +	 * The PAT, PMT, and CAT all set this to 0.
> +	 * Other tables set this to 1.
> +	 */
> +	sdt->header.syntax = 0x1;
> +
> +	/*
> +	 * This is a 16-bit field which serves as a label for identification
> +	 * of the TS, about which the SDT informs, from any other multiplex
> +	 * within the delivery system.
> +	 */
> +	sdt->header.id = transport_stream_id;
> +	sdt->header.current_next = 0x1;
> +
> +	/* ETSI 300 468: indicates changes in the TS described by this table*/
> +	if (update_version_num)
> +		++sdt_version;
> +
> +	sdt->header.version = sdt_version;
> +
> +	sdt->header.one2 = 0x3;
> +	sdt->header.section_id = 0;
> +	sdt->header.last_section = 0;
> +
> +	sdt->network_id = transport_stream_id;
> +	sdt->reserved = 0xff;
> +
> +	sdt->header.section_length =
> +		dummy_fe_sdt_table_comp_sec_len(sdt);
> +}
> +
> +u32 dummy_fe_sdt_write_into(char *buf,
> +			    u32 offset,
> +			    struct dvb_dummy_table_sdt *sdt)
> +{
> +	u32 nbytes = 0; /* the number of bytes written */
> +	u16 sdt_pid = 0x11; /* see ETSI EN 300 468 v1.15.1 p. 11 */
> +	u8 continuity_counter = 0;
> +
> +	struct dvb_dummy_table_sdt_service *service = sdt->service;
> +	struct dvb_dummy_desc *service_desc = (sdt->service) ?
> +					       sdt->service->descriptor :
> +					       NULL;
> +
> +	struct header_write_args h_args = {0};
> +	struct psi_write_args args = {0};
> +	struct desc_write_args d_args = {0};


same here: how much data are you allocating at the Linux small stack?


> +	struct crc32_write_args c_args = {0};
> +
> +	h_args.to = buf;
> +	h_args.offset = offset;
> +	h_args.h = &sdt->header;
> +	h_args.pid = sdt_pid;
> +	h_args.continuity_counter = &continuity_counter;
> +
> +	nbytes += dummy_fe_table_header_write_into(h_args);
> +
> +	args.to = buf;
> +	args.from = sdt + sizeof(struct dvb_dummy_table_header);
> +	args.len = 16;
> +	args.offset = offset + nbytes;
> +	args.pid = sdt_pid;
> +	args.new_psi_section = false;
> +	args.continuity_counter = &continuity_counter;
> +	args.is_crc = false;
> +
> +	/* copy u16 network_id + u8 reserved)*/
> +	nbytes += dummy_fe_ts_psi_write_into(args);
> +
> +	while (service) {
> +		/* u16 service_id + u8 + u16 bitfield */
> +		args.from = service;
> +		args.len = 40;
> +		args.offset = offset + nbytes;
> +
> +		nbytes += dummy_fe_ts_psi_write_into(args);
> +
> +		while (service_desc) {
> +			d_args.to = buf;
> +			d_args.offset = offset + nbytes;
> +			d_args.desc = service_desc;
> +			d_args.pid = sdt_pid;
> +			d_args.continuity_counter = &continuity_counter;
> +			nbytes += dummy_fe_desc_write_into(d_args);
> +
> +			service_desc = service_desc->next;
> +		}
> +
> +		service = service->next;
> +	}

Protect against buffer overflows.

> +
> +	c_args.to = buf;
> +	c_args.offset = offset + nbytes;
> +	c_args.pid = sdt_pid;
> +	c_args.continuity_counter = &continuity_counter;
> +
> +	nbytes += table_section_crc32_write_into(c_args);
> +
> +	return nbytes;
> +}
> +
> +void dummy_fe_sdt_table_destroy(struct dvb_dummy_table_sdt *sdt)
> +{
> +	struct dvb_dummy_table_sdt_service *curr_service = sdt->service;
> +	struct dvb_dummy_table_sdt_service *tmp_service = NULL;
> +	struct dvb_dummy_desc *curr_desc = (sdt->service) ?
> +					   sdt->service->descriptor : NULL;
> +	struct dvb_dummy_desc *tmp_desc = NULL;
> +
> +	while (curr_service) {
> +		curr_desc = curr_service->descriptor;
> +
> +		while (curr_desc) {
> +			/* clear all descriptors for the service */
> +			tmp_desc = curr_desc;
> +			curr_desc = curr_desc->next;
> +			dummy_fe_desc_destroy(tmp_desc);
> +			kfree(tmp_desc);
> +		}
> +
> +		/* then clear the current service */
> +		tmp_service = curr_service;
> +		curr_service = curr_service->next;
> +		kfree(tmp_service);
> +	}
> +}
> +
> +struct dvb_dummy_table_sdt_service*
> +dummy_fe_sdt_service_init(struct dvb_dummy_table_sdt_service *head,
> +			  u16 service_id)
> +{
> +	struct dvb_dummy_table_sdt_service *service;
> +
> +	service = kzalloc(sizeof(*service), GFP_KERNEL);
> +
> +	/*
> +	 * ETSI 300 468: this is a 16bit field which serves as a label to
> +	 * identify this service from any other service within the TS.
> +	 * The service id is the same as the program number in the
> +	 * corresponding program_map_section
> +	 */
> +	service->service_id = service_id;
> +	service->EIT_schedule = 0x0; /* TODO */
> +	service->EIT_present_following = 0x0; /* TODO */
> +	service->reserved = 0x3f; /* all bits on */
> +	service->free_CA_mode = 0x0; /* not scrambled */
> +	service->running_status = RUNNING;
> +
> +	if (head) {
> +		while (head->next)
> +			head = head->next;
> +
> +		head->next = service;
> +	}
> +
> +	return service;
> +}
> +
> +void
> +dummy_fe_sdt_service_destroy(struct dvb_dummy_table_sdt_service *service)
> +{
> +	struct dvb_dummy_table_sdt_service *curr = service;
> +	struct dvb_dummy_table_sdt_service *tmp = NULL;
> +
> +	while (curr) {
> +		tmp = curr;
> +		curr = curr->next;
> +		kfree(tmp);
> +	}
> +}
> +
> +void
> +dummy_fe_sdt_service_assign(struct dvb_dummy_table_sdt *sdt,
> +			    struct dvb_dummy_table_sdt_service *service)
> +{
> +	if (sdt->service)
> +		/* clean up old services */
> +		dummy_fe_sdt_service_destroy(sdt->service);
> +
> +	sdt->service = service;
> +
> +	sdt->header.section_length = dummy_fe_sdt_table_comp_sec_len(sdt);
> +}
> +
> +void
> +dummy_fe_pmt_create_section_for_each_pat_entry(struct dvb_dummy_table_pat *pat,
> +					       struct dvb_dummy_table_pmt *sec)
> +
> +{
> +	/*
> +	 * PMTs contain information about programs. For each program,
> +	 * there is one PMT
> +	 */
> +	struct dvb_dummy_table_pat_program *program = pat->program;
> +	u32 i = 0;
> +
> +	while (program) {
> +		dummy_fe_pmt_table_init(&sec[i],
> +					false,
> +					sec[i].header.id,
> +					0);
> +
> +		++i;
> +		program = program->next;
> +	}
> +}
> diff --git a/drivers/media/dvb-frontends/dvb_dummy_fe_psi.h b/drivers/media/dvb-frontends/dvb_dummy_fe_psi.h
> new file mode 100644
> index 000000000000..17118481148f
> --- /dev/null
> +++ b/drivers/media/dvb-frontends/dvb_dummy_fe_psi.h
> @@ -0,0 +1,287 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef DVB_DUMMY_FE_PSI_H
> +#define DVB_DUMMY_FE_PSI_H
> +
> +#include <linux/types.h>
> +
> +/*
> + * all section lengths start immediately after the 'section_length' field
> + * see ISO/IEC 13818-1 : 2000 and ETSI EN 300 468 V 1.10.1 for
> + * reference
> + */
> +#define PAT_LEN_UNTIL_LAST_SECTION_NUMBER 40
> +#define PAT_MAX_SECTION_LEN 1021
> +#define PMT_LEN_UNTIL_PROGRAM_INFO_LENGTH 72
> +#define PMT_MAX_SECTION_LEN 1021
> +#define SDT_LEN_UNTIL_RESERVED_FOR_FUTURE_USE 64
> +#define SDT_MAX_SECTION_LEN 1021
> +
> +enum dvb_dummy_descriptors {
> +	SERVICE_DESCRIPTOR = 0x48,
> +};
> +
> +enum dvb_dummy_stream_types {
> +	ISO_IEC_13818_3_AUDIO = 0x4,
> +};
> +
> +struct dvb_dummy_desc {
> +	u8 type;
> +	u8 length;
> +	struct dvb_dummy_desc *next;
> +	u8 data[];
> +} __packed;
> +
> +struct dvb_dummy_desc_service {
> +	u8 type;
> +	u8 length;
> +	struct dvb_desc *next;
> +
> +	u8 service_type;
> +	char *name;
> +	char *name_emph;
> +	char *provider;
> +	char *provider_emph;
> +} __packed;
> +
> +struct dvb_dummy_table_header {
> +	u8  table_id;
> +	union {
> +		u16 bitfield;
> +		struct {
> +			u16 section_length:12;
> +			u8  one:2;
> +			u8  zero:1;
> +			u8  syntax:1;
> +		} __packed;
> +	} __packed;
> +	u16 id;			/* TS ID */
> +	u8  current_next:1;
> +	u8  version:5;
> +	u8  one2:2;
> +
> +	u8  section_id;		/* section_number */
> +	u8  last_section;		/* last_section_number */
> +} __packed;
> +
> +struct dvb_dummy_table_pat_program {
> +	u16 service_id;
> +	union {
> +		u16 bitfield;
> +		struct {
> +			u16 pid:13;
> +			u8  reserved:3;
> +		} __packed;
> +	} __packed;
> +	struct dvb_dummy_table_pat_program *next;
> +} __packed;
> +
> +struct dvb_dummy_table_pat {
> +	struct dvb_dummy_table_header header;
> +	u16 programs;
> +	struct dvb_dummy_table_pat_program *program;
> +} __packed;
> +
> +struct dvb_dummy_table_sdt_service {
> +	u16 service_id;
> +	u8 EIT_present_following:1;
> +	u8 EIT_schedule:1;
> +	u8 reserved:6;
> +	union {
> +		u16 bitfield;
> +		struct {
> +			u16 desc_length:12;
> +			u16 free_CA_mode:1;
> +			u16 running_status:3;
> +		} __packed;
> +	} __packed;
> +	struct dvb_dummy_desc *descriptor;
> +	struct dvb_dummy_table_sdt_service *next;
> +} __packed;
> +
> +struct dvb_dummy_table_sdt {
> +	struct dvb_dummy_table_header header;
> +	u16 network_id;
> +	u8  reserved;
> +	struct dvb_dummy_table_sdt_service *service;
> +} __packed;
> +
> +enum service_running_status {
> +	RUNNING,
> +};
> +
> +enum service_type {
> +	/* see ETSI EN 300 468 v1.15.1 p. 77 */
> +	DIGITAL_TELEVISION_SERVICE = 0x1,
> +};
> +
> +struct dvb_dummy_table_pmt_stream {
> +	u8 type;
> +	union {
> +		u16 bitfield;
> +		struct {
> +			u16 elementary_pid:13;
> +			u16 reserved:3;
> +		} __packed;
> +	} __packed;
> +	union {
> +		u16 bitfield2;
> +		struct {
> +			u16 desc_length:10;
> +			u16 zero:2;
> +			u16 reserved2:4;
> +		} __packed;
> +	} __packed;
> +	struct dvb_dummy_desc *descriptor;
> +	struct dvb_dummy_table_pmt_stream *next;
> +} __packed;
> +
> +struct dvb_dummy_table_pmt {
> +	struct dvb_dummy_table_header header;
> +	union {
> +		u16 bitfield;
> +		struct {
> +			u16 pcr_pid:13;
> +			u16 reserved2:3;
> +		} __packed;
> +	} __packed;
> +
> +	union {
> +		u16 bitfield2;
> +		struct {
> +			u16 desc_length:10;
> +			u16 zero3:2;
> +			u16 reserved3:4;
> +		} __packed;
> +	} __packed;
> +	struct dvb_dummy_desc *descriptor;
> +	struct dvb_dummy_table_pmt_stream *stream;
> +} __packed;
> +
> +struct psi_write_args {
> +	void *to;
> +	void *from;
> +	size_t len; /* how much to write */
> +	u32 offset; /* where to start writing in the buffer */
> +	u16 pid; /* TS packet ID */
> +	bool new_psi_section; /* set when starting a table section */
> +	u8 *continuity_counter; /* TS: incremented when section gets split */
> +	bool is_crc; /* set when writing the CRC at the end */
> +};
> +
> +struct desc_write_args {
> +	void *to;
> +	u32 offset;
> +	struct dvb_dummy_desc *desc;
> +	u16 pid;
> +	u8 *continuity_counter;
> +};
> +
> +struct crc32_write_args {
> +	void *to;
> +	u32 offset;
> +	u16 pid;
> +	u8 *continuity_counter;
> +};
> +
> +struct header_write_args {
> +	void *to;
> +	u32 offset;
> +	struct dvb_dummy_table_header *h;
> +	u16 pid;
> +	u8 *continuity_counter;
> +};
> +
> +struct dvb_dummy_desc *dummy_fe_desc_init(struct dvb_dummy_desc *head,
> +					  u8 type,
> +					  u8 length);
> +
> +void dummy_fe_pat_table_init(struct dvb_dummy_table_pat *pat,
> +			     bool update_version_num,
> +			     u16 transport_stream_id);
> +
> +struct dvb_dummy_table_pat_program*
> +dummy_fe_pat_program_init(struct dvb_dummy_table_pat_program *head,
> +			  u16 service_id,
> +			  u16 pid);
> +
> +struct dvb_dummy_table_pmt_stream*
> +dummy_fe_pmt_stream_init(struct dvb_dummy_table_pmt_stream *head,
> +			 enum dvb_dummy_stream_types stream_type,
> +			 u16 es_pid);
> +
> +void dummy_fe_pmt_table_init(struct dvb_dummy_table_pmt *pmt,
> +			     bool update_version_num,
> +			     u16 program_number,
> +			     u16 pcr_pid);
> +
> +void
> +dummy_fe_sdt_table_init(struct dvb_dummy_table_sdt *sdt,
> +			bool update_version_num,
> +			u16 transport_stream_id);
> +
> +struct dvb_dummy_table_sdt_service*
> +dummy_fe_sdt_service_init(struct dvb_dummy_table_sdt_service *head,
> +			  u16 service_id);
> +
> +void
> +dummy_fe_desc_destroy(struct dvb_dummy_desc *desc);
> +
> +void
> +dummy_fe_pat_program_destroy(struct dvb_dummy_table_pat_program *p);
> +
> +void
> +dummy_fe_pat_table_destroy(struct dvb_dummy_table_pat *p);
> +
> +void
> +dummy_fe_pmt_stream_destroy(struct dvb_dummy_table_pmt_stream *s);
> +
> +void
> +dummy_fe_pmt_table_destroy(struct dvb_dummy_table_pmt *pmt);
> +
> +void
> +dummy_fe_sdt_table_destroy(struct dvb_dummy_table_sdt *sdt);
> +
> +void
> +dummy_fe_sdt_service_destroy(struct dvb_dummy_table_sdt_service *service);
> +
> +void
> +dummy_fe_desc_destroy(struct dvb_dummy_desc *desc);
> +
> +void
> +dummy_fe_pat_program_destroy(struct dvb_dummy_table_pat_program *p);
> +
> +void
> +dummy_fe_sdt_service_assign(struct dvb_dummy_table_sdt *sdt,
> +			    struct dvb_dummy_table_sdt_service *service);
> +
> +void dummy_fe_desc_assign(struct dvb_dummy_desc *desc,
> +			  struct dvb_dummy_desc *desc_ptr,
> +			  u16 *desc_length);
> +
> +void dummy_fe_pat_program_assign(struct dvb_dummy_table_pat *pat,
> +				 struct dvb_dummy_table_pat_program *p);
> +
> +void dummy_fe_pmt_stream_assign(struct dvb_dummy_table_pmt *pmt,
> +				struct dvb_dummy_table_pmt_stream *s);
> +void
> +dummy_fe_pmt_create_section_for_each_pat_entry(struct dvb_dummy_table_pat *pat,
> +					       struct dvb_dummy_table_pmt *sec);
> +
> +u16 dummy_fe_pmt_get_pid(struct dvb_dummy_table_pmt *section,
> +			 struct dvb_dummy_table_pat *pat);
> +
> +u32 dummy_fe_pat_write_into(char *buf,
> +			    u32 offset,
> +			    struct dvb_dummy_table_pat *pat);
> +
> +u32 dummy_fe_sdt_write_into(char *buf,
> +			    u32 offset,
> +			    struct dvb_dummy_table_sdt *sdt);
> +
> +u32 dummy_fe_pmt_write_into(char *buf,
> +			    u32 offset,
> +			    struct dvb_dummy_table_pmt *pmt,
> +			    u16 pid);
> +
> +#endif // DVB_DUMMY_FE_PSI_H



Thanks,
Mauro


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